What we learned about the Global Burden of Disease?

Kofi Annan, the former Secretary-General of the United Nations, observed that knowledge is power and information is liberating. Indeed, the collection, analysis and dissemination of data and information should not be seen only as an instrument of scientific inquiry but more importantly, as a critical tool for guiding the formulation and implementation of policies to address complex problems in society.

Last week at George Washington University in Washington, D.C., we had the opportunity to participate in the presentation of the findings of the Institute of Health Metrics and Evaluation’s (IHME) Global Burden of Diseases, Injuries, and Risk Factors Study 2015 (GBD). Published as part of a dedicated issue of The Lancet, the GBD provides a picture of population health dynamics across the world over the last 25 years. The evidence generated by the GBD on the basis of comparable health estimates by year, age, and sex for 249 causes from 195 countries and territories, represents an important “global public good” as it informs current and future health policy discussions around the world.

What are some of the key findings of the GBD 2015?

Globally, life expectancy at birth has increased significantly from 61.7 years in 1980 to 71.8 years in 2015. It is particularly noteworthy that several countries in sub-Saharan Africa had large gains in life expectancy after years of high loss of life due to HIV/AIDS. These gains largely reflect increased access to diagnosis and treatment. Violence and conflict, however, contributed to rising mortality and stagnation and decline in life expectancy in some regions, such as the Middle East. This phenomenon was clearly observed in Syria, where male life expectancy dropped by 11.3 years to 62.5 years over the 2005-2015 period.

Over the 1990-2015 period, the world as a whole has been undergoing a health transition (Fig. 1 below). Whereas total deaths and age-standardized death rates due to communicable (e.g., HIV/AIDS, malaria), maternal, neonatal, and nutritional conditions significantly declined, marked increases were recorded in total deaths and age-standardized death rates from non-communicable diseases (NCD). Vascular disease, cancers, and chronic respiratory diseases are the leading causes of NCD deaths; the relative importance of Alzheimer’s disease and other dementias as a cause of death increased as well, reflecting the aging of the population. Age-standardized death rates from injuries declined, although interpersonal violence and armed conflicts claimed a higher number of lives in 2015.

Figure 1: Leading Causes of Global YLLs for both sexes, 1990, 2005, 2015

Non-fatal outcomes of disease and injury detract from the ability of the world’s population to live in full health. As populations grow and increase in average age, the total burden of disability is rising quickly. As a result, the number of people living with sequelae of diseases and injuries is increasing. Between 2005-2015, NCDs account for 18 of the leading 20 causes of age-standardized years lived with disability (YLDs). GBD also confirms the large contribution of mental and substance use disorders to global disability, which raises the importance of achieving mental health parity in the provision of health and social services.

In terms of environmental, behavioral, occupational, and metabolic risk factors and their attributable burden of disease, the GBD illustrates a health risk transition across the world. Attributable disability-adjusted life years declined for environmental risks such as unsafe water, sanitation, and hygiene, as well as household air pollution, micronutrient deficiencies, childhood undernutrition. These trends, which experienced a significant decline as countries develop, are driving the notable reduction in the relative importance of infectious diseases as leading causes of ill health and death. By contrast, some health risk factors are growing worse as countries develop contributing to the rising burden of NCDs. Globally, the leading risk factors are high systolic blood pressure, smoking, high blood sugar level, and high body-mass index. In some regions, alcohol and drug use as well as exposure to occupational risks and air pollution are also important risks.

Overall, the findings of GBD 2015 convey some good news, but they also point to emerging challenges as well as opportunities for action. In moving the global health agenda forward, an important message from the GBD that we should keep in mind is that development drives, but does not determine, the health status of the population. As observed worldwide, more developed countries tend to be healthier than less developed ones, but countries are much healthier than expected given their level of development, such as Ethiopia, China, Cuba, and Spain.

For those engaged in policy dialogue, program design and implementation at the global, regional and country levels, the above message implies that the effective use of the wealth of data and information from GBD demands that we assess and try to understand the particular drivers of the observed trends in specific contexts. In doing so, we must keep in mind that a close relationship exists in cause, course, and outcome between communicable diseases, maternal, perinatal, and nutritional conditions, and NCDs--they are part of the same biological continuum. This reflects common underlying social conditions, such as poverty and unhealthy environments, and commonalities across disease groups in causation, co-morbidity, and care needs. Frequently, both communicable diseases and NCDs, or a combination of risk factors, co-exist in the same individual, and one can increase the risk or impact of the other, as happens for example with diabetes and tuberculosis. Similarly, factors like maternal health, the intra-uterine environment, and low birthweight can have long-term consequences for developing NCDs.

This inescapable reality reinforces the need for integrated approaches at the country level that address functions (prevention, treatment, and care) rather than disease categories. And given the multisectoral nature of health conditions, actions that reach beyond the health system, such as fiscal and regulatory policies, have to be essential components of an effective arsenal of interventions to improve health conditions globally.